Nature is a delicate balancing act, says Bill Nye the Science Guy. It's important we understand that the same system making Earth warm enough to live on is also driving climate change.

Billy Wickman: Hello, Mr. Nye. Happy Tuesday. My name is Billy. I'm a big fan, and I have a question about climate change. If the photons from the sun are trapped in our atmosphere by our greenhouse gases, then how come those same greenhouse gases don't block photons from the sun from ever entering our atmosphere? Is there some sort of weird cosmic one-way road sign? Thank you.

Bill Nye: Billy. Billy. Billy. You have chanced on like the most important idea right now in climate science. When you say photons from the sun come in through the atmosphere, that is absolutely true. And they go through, out through, the atmosphere, but not all of them get out at the same energy. Now here's the strange thing about light and electromagnetism. Now bare in mind we are humans trying to understand nature, and if we can't get our heads around this it's our problem. But basically, if you do experiments on waves of lights or electricity, electromagnetic waves you will find waves. If you do experiments on photons of light or electromagnetism you will find particles. You can either detect particles or waves. So both of these ideas have helped us in physics understand nature. So here's what happens.

Light from the sun comes in at wavelengths that our eyes detect very well. It hits the earth and is reradiated, the energy is absorbed by the atoms of soil, of bridges, of the ocean, of ice and reradiated or sent back out again at a longer wavelength — it's a little longer. And I don't know if you know this, but you probably do, what we — you and I — call heat is the same thing as light at a wavelength longer than we see with our eyes. There are a lot of animals that see these wavelengths, but that's not our issue. You've seen it with night vision goggles, those cool images.

So light from the sun passes through the atmosphere, hits the earth — all these different materials — and is reradiated at a longer wavelength that carbon dioxide, methane and some other gases hold in. The visible light at the faster wavelength goes through, the heat at the longer wavelength does not go through to a limited extent, to a significant extent. And that's how the Earth is warm enough for us to live. And because we put so much extra greenhouse gas via various species in the atmosphere, the world is getting warmer faster than it's ever gotten before. It's a great question Billy. That is the essence of this: passes through at one wavelength, starts to go back out at a longer wavelength that is held in by the greenhouse gases. This is the fundamental idea in climate science. Carry on!

Nature is a delicate balancing act, says Bill Nye the Science Guy. It's important we understand that the same system making Earth warm enough to live on is also driving climate change. According to Nye, scientists understand energy emanating from the sun in two distinct ways: as photons and waves.

When you measure sunlight as waves, you notice that wavelengths of sunlight are shorter when they enter the Earth's atmosphere, and grow in length when they try to leave, after being irradiated by Earth objects: soil, ice, concrete, office buildings, etc. Herein lies the primary mechanism of climate change: atmospheric gases like carbon dioxide and methane prevent longer-wave light from passing through, thus becoming trapped inside Earth's atmosphere. These so-called greenhouse gases trap light only when it tries to exit the Earth.

Bill Nye is a strong advocate for climate change awareness. He has publicly encouraged candidates for office to confront the science behind climate change and petitioned the media to ask candidates about their position on human-caused warming. Nye is the author of Undeniable: Evolution and the Science of Creation.

Even the optimists among us would have to admit 2018 was a challenging year. The fractured world that became the focus of our 2018 Annual Meeting a year ago came under further pressure from populist rhetoric and rising nationalist agendas. At the same time, the urgent need for coordinated global action in areas such as climate change, inequality and the impact of automation on jobs became more intense.